A "nightmare" dispute over two farms worth $8 million has pitted brother against brother and threatened a Wairarapa family's legacy.

Malcolm and Alastair Jaspers have been at loggerheads since their father, Thomas Jaspers, became too ill to work the Martinborough properties in 2004.

Run as a single 400-hectare sheep-and-beef block, the farms are owned by the Jaspers Family Trust. Malcolm, 42, and Alastair, 41, are the beneficiaries.

Since 2008 the pair have lodged legal proceedings against each other, including an attempt by Malcolm to "restrain" his brother's access to the farms.

After mediation, the farms are now being put up for sale, and Alastair said both could be lost to the family.

"It's not just our father's legacy but it's also our grandfather's legacy that's at stake," he said. "I'd hoped that we would be bigger than that and that we could put it behind us, but that hasn't happened. It's been a complete nightmare really."

In April, the trust was placed in control of an appointed solicitor, John Greenwood, who was given instructions to sell the properties - known as Tawaha and The Cutting - and distribute the proceeds equally.

However, in August, Alastair applied to the trust to allow him to buy one farm, The Cutting, for an agreed price.

His brother opposed the move, stating in an affidavit that he intended to tender for both farms.

In a High Court judgment delivered last month, Justice Stephen Kos dismissed Alastair's application, meaning the farms will now be put up for sale.

Alastair said an answer to the dispute was "sitting right there in front of us".

"Our situation was the easiest we'd ever come across. There's two brothers, we're both farmers, and there were two farms.

"One gets one farm and one gets the other plus a little bit of cash.

"It's hard to understand how it actually got to this stage."

Their father died late last month aged 86, after operating the farm for 35 years.

"[Dad] said he did not want this going to court," Alastair said.

Blair Stevens, of Property Brokers, said marketing of the properties would begin next week, with an auction scheduled for early December in Greytown.

Malcolm Jaspers declined to comment, referring questions to his lawyer, who could not be contacted.